qjs fails to output content via stdout to pipe or non-console receiver

[harig]

After 72d4587 content emitted by qjs (via console.log/print etc. ) to stdout fails to reach a receiver through a pipe or other process reading from its stdout on Windows 10.
For example, if we run the following inside cmd.exe
qjs -e "print(1);"
will print 1
qjs -e "print(1);" | cat
will not output anything.
Similar issue can be seen with qjs launched as a process and some other program reads its output.

[bnoordhuis]

Yeah, I'm not too surprised that broke. Pull request welcome.

You can use something like this to detect whether stdout refers to the console:

#ifdef _WIN32
int isatty(int fd) { // if (isatty(1)) { /* ... */ } else { /* ... */ }
   DWORD mode;
   HANDLE handle = (HANDLE)_get_osfhandle(fd);
   if (GetFileType(handle) == FILE_TYPE_CHAR)
       if (GetConsoleMode(handle, &mode))
           return 1;
   return 0;
}
#endif

There's one very annoying gotcha though: _get_osfhandle() asserts in msvcrt debug builds if the file descriptor is invalid. You can suppress it with _CrtSetReportHook but it's super kludgy and libraries shouldn't touch that.

Hooking it in qjs.c is fine but not in quickjs-libc.c.

[bnoordhuis]

@harig can you test #642 and report back?